Earlier in 2010, the famous physicist Stephen Hawking made headlines with the controversial remark that our search for extra-terrestrial intelligence is putting Earth at too great a risk, since it may provoke an unwanted first contact with hostile aliens. In his popular television documentary series “Stephen Hawking’s Universe,” Hawking explained that sending messages into the stars could risk attracting attention from “nomads, looking to conquer and colonize”: in other words, an advanced extraterrestrial civilization which had used up the resources on its own homeworld and now prowls the galaxy in search of new, exploitable systems.
If we accidentally attract their attention, Hawking notes, the resulting encounter would almost certainly go very poorly for us. The technological disparity between, say, early twenty-first century Earth and an extremely advanced spacefaring race of scavengers would be much greater than that between fifteenth-century Europe and the civilizations of the Americas – and that encounter, Hawking notes, “didn’t turn out very well for the Native Americans.”
Of course, the likelihood that the search for extra-terrestrial intelligence will attract the wrong sort of attention is incredibly low. However, Hawking’s concerns are not new. In the past, similarly minded critics have pointed out that while this risk does seem low, the chances of identifying an alien race in the first place are very low. At best, SETI is simply a waste of money; at worst, it risks exposing us to an alien race that could threaten our very survival.
Not everyone is convinced by Hawking’s remarks. Some consider them insulting to humans: after all, by the time our radio signals reach distant stars (which would take mere decades if an alien ship is close by, but more likely centuries or even millennia), and by the time they arrange to travel here (probably at much less than light-speed, meaning even more decades or centuries), humanity will either have killed itself off due to war or climate change, or we will have progressed, too, to the point where we might well be a technological match for any aliens that come our way.
Moreover, the “alien scavenger” hypothesis does have some weaknesses. It is quite plausible that, if alien civilizations do exist, at least some of them are scavengers, having lost or exhausted the resources of their homeworld and set out in search of alternatives. (It may also be that they are searching for some particular mineral not found on their homeworld, as was the premise for the recent blockbuster “Avatar.”) However, from what we know about other objects in the solar system, it seems unreasonable to suppose that the presence of life is necessarily tied to the presence of the sort of valuable resources aliens might be interested in. Even here, scientists recognize that some very useful mining activities could be carried out on the Moon and on asteroids – if, of course, we had the means to travel there and set up mining outposts, which we currently don’t. There’s no reason to believe that Earth is in any way special, unless what these scavengers are really looking for is fresh meat for their dinner table – a truly chilling scenario.
Still, Hawking’s warning is a useful reminder. For years, the apparently very high odds that there should be a significant number of other alien civilizations in our universe, given hundreds of billions of stars around which such life could develop, have been challenged by what is known as the Fermi paradox: if the galaxy is teeming with intelligent life, at least some of it should be old enough and advanced enough that we would see evidence of their activities, even if we haven’t actually seen any individual aliens. Yet we have not seen any evidence (or at least none has ever been confirmed). Logically, this means we haven’t yet figured out all the rules of the game: clearly either something is preventing intelligent species from emerging as often as we think they should, or something is making them disappear once they have appeared.
The simplest solution (and therefore the most likeliest) is simply that we’ve misunderstood how truly unusual humanity is in the cosmos. However, Hawking’s fears point to another solution to the Fermi paradox: the hypothesis that our galaxy is the hunting ground of a superpredator species, which hunts out and harvests other intelligent civilizations in much the same way as we domesticate cattle, hunt game, fish, and kill whales. If such a superpredator is lurking, then the reason we have not been able to find other intelligent civilizations is because most have been wiped out, and the survivors are deliberately staying quiet for their own protection. And, of course, if that’s the case, then we should do the same.
Unfortunately, despite Hawking’s warning, if such a grim fate does lie in store for humanity than stopping the search for extra-terrestrial intelligence may not help matters much anyways. We already send a considerable number of signals into space, thanks in particular to analog broadcast television (although that source will probably come to an end soon). For all we know, Hawking’s scavenger-predators have already located Earth and are on their way. Certainly it is a question worth debating further before deliberate attempts, even unlikely ones, are made to contact alien civilizations.
